1. Field of the Invention
This invention relates to magnetic recording and more particularly, to a magnetic recording medium which is suitable for use in horizontal magnetic recording systems. Typical of the medium is a magnetic disc of the type which is recorded and reproduced by the use of a flying ring head. The invention also relates to a method for making such a recording medium.
2. Description of the Prior Art
For high density recording, magnetic recording mediums using metallic thin films have been recently developed and proposed. The thin films are formed on a substrate by sputtering, electroplating or electroless plating of magnetic materials such as, for example, Co, Co-Ni, Co-P, Co-Ni-P and the like.
However, this type of magnetic recording medium has a poor corrosion resistance and is not suitable for use under high humidity conditions. To avoid this, there has been proposed the provision of a corrosion-resistant layer on the magnetic thin layer. This is not advantageous, however, in view of the rise in cost because of the additional step of forming the corrosion-resistant layer. Moreover, the provision of the layer will increase the spacing of a magnetic head, which undesirably brings about a lowering of reproduction output.
Attention has now been paid to Co-Cr alloys because of the good corrosion resistance. Co-Cr alloys have also good vertical magnetic anisotropy, so that these alloys have been intensively studied as suited for vertical magnetization recording systems which involve little problem of self-demagnetization.
For the improvement of the vertical magnetic anisotropy, there has been proposed a high speed precipitation method in which Co-Cr magnetic grains are precipitated at a high speed of, for example, 5000 to 8000 angstrom/minute in an atmosphere of a gas containing 5.times.10.sup.-6 Torr. of molecular oxygen, by which a Co-Cr vertical magnetization film containing about 2 to 8 atomic percent of segregated oxygen is formed on a substrate (Japanese Laid-open Patent Application No. 59-17216).
However, the above type of magnetic medium is disadvantageous in that when it is applied to a recording and reproducing apparatus using, for example, a magnetic ring head and particularly a flying ring head, the reproduction output becomes small. In this sense, the magnetic recording medium is not necessarily satisfactory with respect to recording and reproducing characteristic properties.